The present invention relates generally to the production of bent glass sheets and, more particularly, to an improved method of and apparatus for bending specially configurated glass sheets.
Bent sheets of glass are commonly used as glazing closures in vehicles such as automobiles and the like. For such applications, the glass sheets must be bent to precisely defined curvatures dictated by the configuration and size of the vehicle openings and the overall styling of the vehicle. At the same time, it is important that the bent sheets meet stringent optical requirements and that the viewing area of the window or closure be free of optical defects that would tend to interfere with the clear viewing therethrough. Further, bent glass sheets intended for use as glazing closures in vehicles are subjected to an additional heat treatment to temper the glass for strengthening the same and increasing the resistance thereof to damage resulting from impact.
Generally, the commercial production of bent, tempered sheets of glass for automotive glazing closures includes heating pretrimmed flat sheets of glass to the softening temperatures thereof, bending the heated sheets to a desired curvature between a pair of complementary shaped press members and then chilling the bent sheets in a controlled manner to a temperature below the annealing range of glass.
Very often, the press members are of outline or ring-type construction comprised of shaping rails conforming in outline to the glass sheets to be bent and are provided with opposed complementary shaping surfaces to impart the desired curvature to the sheets. These shaping rails engage only the marginal edge portions of the sheets to be bent, the remainder or central portions of the glass sheets located inwardly of the marginal edge portions being unrestrained and allowed to sag.
While such outline type press members have admirably served the purposes for which they were designed in bending glass sheets of conventional shapes, they have limitations in forming unusual or specially configurated glass shapes, such as glazing closures having longitudinal reverse bends in the direction opposite to sagging for example.